Effects of antioxidant enzymes and bioaccumulation in eels ( Anguilla japonica ) by acute exposure of waterborne cadmium
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RESEARCH ARTICLE
Open Access
Effects of antioxidant enzymes and bioaccumulation in eels (Anguilla japonica) by acute exposure of waterborne cadmium Tae-Young Ahn1, Hee-Ju Park2, Jun-Hwan Kim3 and Ju-Chan Kang2*
Abstract This study was conducted to evaluate the acute effects of waterborne cadmium exposure on bioaccumulation and antioxidant enzymes in eels (Anguilla japonica) and to determine the median lethal concentration (LC50). Fish were exposed to different cadmium concentrations (0, 0.15, 0.30, 0.61, 1.83, 3.08, 3.67, 4.29, and 5.51 mg L−1) for 96 h. The LC50 of A. japonica to cadmium was 3.61 mg L−1. Cadmium accumulation generally increased in tissues with increasing waterborne cadmium concentrations. At ≥ 1.83 mg L−1 exposure, all tissues accumulated significant cadmium concentrations compared with the control group, in the order of kidney > liver > gill > spleen > muscle. Measurements of variation in actual cadmium concentrations showed that a reduction of the metal in experimental water was related to cadmium accumulation in tissues. As activity alteration of antioxidant enzymes for reactive oxygen species, superoxide dismutase and catalase activities increased at ≥ 0.61 mg L−1 significantly, glutathione peroxidase and glutathione S-transferase activities were not significantly changed. The results of this study suggest that acute exposure to waterborne cadmium is potentially fatal to A. japonica due to the metal’s major accumulation in various tissues and the effect of antioxidant enzyme activity. Keywords: Cadmium, Anguilla japonica, Acute toxicity, LC50, Bioaccumulation, Antioxidant enzyme
Introduction Metals naturally exist in aquatic ecosystems, but side effects from industrialization have resulted in excessive concentrations. Exposure to high metal levels may negatively affect fish and other aquatic organisms, hampering physiological functions, growth rate, and reproduction, or even increasing mortality (Reddy and Reddy 2013; Öz 2018; Öz et al. 2018). Cadmium is a particularly widespread and toxic example that is documented to accumulate in exposed organisms; it is used primarily in alloys, pigments, electroplating, and batteries (Bryan 1976; Farag et al. 1995; Adriano 2001; Javed 2003). In fish, Cd disrupts Ca metabolism through competition for transport sites on the basolateral calcium pumps * Correspondence: [email protected] 2 Department of Aquatic Life Medicine, Pukyong National University, Busan 48513, South Korea Full list of author information is available at the end of the article
of gills (Verbost et al. 1987, 1988, 1989; Pinot et al. 2000). Cd redox activity affects antioxidants, thus reducing protection against oxidative stress, increasing lipid peroxidation, and decreasing DNA synthesis (Okorie et al. 2014). In addition, Cd lowers plasma Na, Cl, and K, leading to hyperglycemia and hypermagnesemia (Larsson et al. 1981; Haux and Larsson 1984; Sjöbeck et al. 1984). Even at low concentrations, Cd deforms tissues and vertebrae, causing respiration abnormalities and death in fish (De Smet
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